Thermally developable diazotype copying materials

ABSTRACT

THERMALLY DEVELOPABLE DIAZOTYPE COPYING MATERIALS COMPRISING A SUPPORT SHEET AND A LIGHT-SENSITIVE LAYER SUPPORTED THEREON, SAID LAYER CONTAINING A LIGHT-SENSITIVE DIAZO COMPOUND WHOSE PRINCIPAL COMPONENT CONSISTS OF ORTHO-CARBOXY BENZENE DIAZONIUM CHLORIDE, SAID LAYER FURTHER CONTAINING A COUPLER, A THERMALLY DECOMPOSABLE ALKALI GENERATING AGENT (AN AGENT ADAPTED TO PROUDUCE AN ALKALINE COMPONENT DUE TO THE HEAT DECOMPOSITION OF SAID AGENT) AND AN ACID STABLIZIER.

United States Patent 3,625,693 THERMALLY DEVELOPABLE DIAZOTYPE COPYINGMATERIALS Takehiko Iwaoka, Tokyo, Japan, assignor to Kabushiki KaishaRicoh, Tokyo, Japan No Drawing. Filed Nov. 3, 1967, Ser. No. 680,358Claims priority, applilcfiiorfil Japan, Nov. 9, 1966,

Int. 01. misc 1/58 US. CI. 96-75 2 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to thermally developa'ble diazotype copying materials having aparticularly improved shelf life, said copying materials carrying alightsensitive layer thereon containing a novel light-sensitive diazocompound which is adapted to display its coupling activity only whensubjected to a temperature which is 100 C. or higher.

DESCRIPTION OF THE PRIOR ART Conventional thermally developablediazotype copying materials employ, as the fundamental componentsconstituting their light-sensitive layers, the following four componentswhich are: a diazo compound, a, coupler and an acid stabilizer, all ofwhich have been used in the socalled dry development copying materialsas well as in the wet development copying materials, and also athermally decomposable alkali generating agent. However, the thermallydecomposable alkali generating agent which is contained as a couplingaccelerator in the copying materials of the prior art had a disadvantagethat it became gradually decomposed during the storage of the copyingmaterials, causing the acid stabilizer to be neutralized, resulting inan elevation of the pH value of the light-sensitive layer andaccordingly causing a premature coupling between the diazo compound andthe coupler to take place. Thus, the storage of the development typecopying materials for an extended period of time results not only in aloss of clear images on the prints obtained, but also gave rise toinstances where the copying materials were no longer usable because ofthe occurrence of the so-called fog effect.

SUMMARY OF THE INVENTION The present invention is concerned withthermally developable diazo-type copying materials which are featured bythe inclusion, in the light-sensitive layerof the following fundamentalcomponent which consists of an ortho-carboxy diazonium compound whichwill be described later.

It is the object of the present invention to eliminate the shortcomingsof the copying materials of the prior art and to provide a copyingmaterial which is of an improved shelf life and which permits the userto obtain a clear image of print, by conducting the development at icean elevated temperature (under heat development conditions; atemperature ranging from C. to 200 C., and a development time rangingfrom 2 to 10 seconds). More specifically, it is the primary object ofthe present invention to provide a thermally developable diazotypecopying material having a markedly improved shelf life. Another objectof the present invention is to provide a light-sensitive diazoniumcompound which is outstandingly suitable for use in thermallydevelopable diazotype copying materials.

The diazo compounds which are used in the present invention can beclassified into the following four groups: (a) Compounds represented bythe general formula:

COOH R1 wherein: R and R are selected from the group consisting ofhydrogen; aryl radicals; alkyl radicals having 1 to 4 carbon atoms; andhydroxy alkyl radicals having 1 to 4 carbon atoms, and X is selectedfrom the group consisting of hydrogen, alkyl radicals having 1 to 4carbon atoms and alkoxy radicals having 1 to 4 carbon atoms.

(b) Compounds represented by the general formula:

wherein: Y is selected from the group consistin of CO--NH, S, and NH-,and X is selected from the group consisting of hydrogen, alkyl radicalshaving 1 to 4 carbon atoms and alkoxy radicals having 1 to 4 carbonatoms.

(c) Compounds represented by the general formula:

CIJOOH wherein:

Y is selected from the group consisting of a morpholino radical, apyrrolidinyl radical and a piperazinyl radical, and

X is selected from the group consisting of hydrogen, alkyl radicalshaving 1 to 4 carbon atoms and alkoxy radicals having 1 to 4 carbonatoms.

((1) Compounds represented by the general formula:

(IJOOH XII wherein: Z is selected from the group consisting of alkoxylradicals having 1 to 4 carbon atoms and X is selected from the groupconsisting of halogen, alkyl radicals having 1 to 4 carbon atoms andalkoxy radicals having 1 to 4 carbon atoms.

These ortho-carboxy diazo compounds represented by the foregoing generalformulas (a) through (d), or more specifically, the compounds whoseprincipal component consists of ortho-carboxy benzene diazonium chlorideare markedly stable even in an alkaline atmosphere and do not give riseto coupling even in the presence of couplers. However, these compoundsgain coupling activity only when subjected to an elevated temperature,and at such time they easily react with the couplers which are incontact with these compounds. In other words, those orthocarboxy diazocompounds enumerated above do not possess coupling activity at normaltemperature, but they gain coupling ability for the first time when theyare heated to 100 C. or higher. Such nature of these particularcompounds has not been elucidated yet. It is presumed, however, that thediazo radical and carboxyl radical contained in said diazo compoundsform a secondary bonding at normal temperature, having a structure whichis quite stable in an alkaline atmosphere and with no coupling activityof their own. It is considered further that, by heating the compounds to100 C. or higher, the aforesaid secondarybonding between these radicalsis destroyed, converting the compounds into such diazo compounds as havecoupling activity, so that in case the heated compounds containing acoupler is placed in an alkaline atmosphere, the compoundsinstantaneously couple with the coupler to form a dyestutf. In thepresent invention, these orthocarboxy diazo compounds are used in theform of borofiuoride or metal double salts such as zinc chloride andcadmium chloride.

Description will next be directed to examples of preparation of thesediazo compounds.

(1) P-dimethylamino-O-carboxy-benzene diazonium chloride-cadmiumchloride double salt P-dimethylamino-O-carboxyl-aniline was dissolved ina solution consisting of 50 cc. of water and 16 gr. of 12 N hydrochloricacid. To this mixed solution which was cooled to a temperature rangingfrom C. to C. was added 3 gr. of sodium nitrite (NaNO The reaction wascompleted at the end of about one hour of continuous stirring at saidtemperature. After filtering the resulting solution, cadmium chloridewas gradually introduced into the filtered solution, with the resultthat a yellow precipitate was formed. After filtering this precipitate,it was recrystallized with water. As the result, the captioned diazocompound having a melting point of 174 C. was obtained.

(2) P-diethyl-m-ethoxy-O-carboxy-benzene diazonium chloride-cadmiumchloride double salt In exactly the same manner as in (l), the captioneddiazo compound was formed from P-diethyl-m-ethoxy-O- carboxy-aniline.

(3 P-benzoylamino-m-ethoxy-O-carboxy-benzene diazonium borofluoride 30gr. of P-benzoylamino-m-ethoxy-O-carboxy-aniline and 9 gr. of sodiumnitrite were dissolved in 50 cc. of water. The resulting solution whichwas cooled to 0 C.- 3 C. was gradually added to 50 cc. of an aqueoussolution containing 20 cc. of undiluted hydrochloric acid (12 N) whichwas held at 0 C.3 C. while stirring the mixture. After the completion ofthis admixture, stirring was continued for 30 minutes, followed by theaddition of sodium fluoborate (NaF B). As a result, a precipitate wasformed. After filtering the precipitate, the latter was recrystallizedwith water. Thus, yellow crystals of the captioned diazo compound havinga melting point of 178 C. was obtained.

(4) P-morpholino-O-carboxy-benzene diazonium chloride-cadmium chloridedouble salt 23 gr. of P-morpholino-O-carboxy-aniline and 25 cc. ofundiluted hydrochloric acid 12 N) were dissolved and dispersed in 100cc. of water. While stirring, the resulting solution held at 0 C.3 C.and 9.0 gr. of sodium nitrite was gradually added thereto. Aftercompletion of the admixture, stirring was continued for about one hour,at the end of which diazotization was completed. Upon the addition ofcadmium chloride to the resulting solution, there was formed a yellowprecipitate. The filtered precipitate was subjected tore-crystallization which was repeated twice. As a result, beautifulyellow crystals of the captioned diazo compound was obtained.

The couplers which are used in the present invention include knowncouplers which have been used in the conventional dry developmentcopying materials and wet development copying materials. They include,for example, 2,3-dihydroxy-naphthalene-6-sodium sulfonate, 1-hydroxy-naphthalene-4-sodium sulphate, R-acid, naphthol AS,2,3-dihydroxy naphthalene, 2,7-dihydroxy naphthalene 3,6-disodiumsulfonate and NW-acid.

Similarly, as the acid stabilizers there can be employed those which'have been used in the conventional dry development copying materialsand wet development copying materials. They include, for example,tartaric acid, citric acid, oxalic acid, malonic acid, nialeic acid,sulphuric acid and phosphoric acid.

Thermally decomposable alkali generating agents which are used in thepresent invention are such that they are neutral at normal temperature,but they produce alkaline substances when heated to C. or higher.

The thermally decomposable alkali generating agents include:

(a) Urea and its derivatives: urea, phenyl-urea, methylurea, ethyl-urea,hydroxyethyl-urea, acetyl-urea, 1,3- dimethyl-urea.

(b) Thiourea and its derivatives: thiourea, thioacetamide,

guanyl-o-methyl-isothiourea, methyl-isothiourea.

(c) Guanidine and its derivatives: guanidine, amino-guanidine,guanyl-urea, biguanidine, methyl-biguanidine, omethyl-guanyl urea,cyanoguanidine.

(d) Acid amide compounds: acetamide, acryl-amide, propionamide,butylamide, malonamide, salicylamide.

(e) Salts which were produced with trichloroacetic acid and basiccomponent: sodium trichloroacetate, potassium trichloroacetate, ammoniumtrichloroacetate, calcium trichloroacetate,dimethylarnine-trichloroacetate, diethylamine trichloroacetate,monomethylamine-trichloroacetate, triethanolamine-trichloroacetate,guanidine-trichloroacetate, aminoguanidine-trichloroacetate.

These thermally decomposable alkali generating agents are added eitherindependently or in combination of two or more of them to thelight-sensitive layer.

The thermally developable diazotype copying materials of the presentinvention are manufactured by first preparing a solution adapted forforming a light-sensitive layer by mixing, with appropriate ratio byweight, one of the aforesaid diazo compounds, one of the aforesaidcouplers, one of the aforesaid acid stabilizers and one or combinationof two or more of the aforesaid thermally decomposable alkali generatingagents, thereafter applying this solution uniformly onto the upper faceof the supporting sheet in an amount in the range of from 40 to 60gr./m. and then drying the coated sheet. The supporting sheets are notrestricted to paper alone, but they can be selected, as desired, fromvarious sheet materials such as precoated paper cloths and plasticfoils.

As has been described above, the thermally developable diazotype copyingmaterials of the present invention carry thereon a light-sensitive layercontaining a novel diazo compound 'which does not display its couplingability unless heated to 100 C. or higher. Therefore, there takes placeabsolutely no premature coupling phenomenon between the diazo compoundand the coupler even after the copying materials have been stored for anextended period of time. Besides, by the use of the copying materials ofthe present invention in taking copies of originals, there are formedvery clear images on the prints by subjecting the exposed sheets to heatdevelopment at a temperature ranging from 100 C. to 200 C. for two toten seconds. Moreover, when the exposed copying materials of the presentinvention are developed in ammonia gas or an alkaline developingsolution in a manner similar to that for the conventional dry or wetdevelopment copying materials, there takes place hardly any couplingphenomenon between the diazo compounds and the couplers, andaccordingly, no color development is effected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1P-dimethylamino-ortho-carboxy-benzene diazonium chloride-zinc chloridedouble salt 1.0 2,3-dihydroxy-naphthalene-6-sodium sulphonate 2.0Tartaric acid 1.0 Urea 20.0 Water 100.0

A solution consisting of the above composition was uniformly appliedonto the face of a supporting sheet to an extent of 50 gr./m. followedby drying. As the result, a thermally developable diazotype copyingmaterial having a markedly improved shelf life was obtained. An originalwas placed on this copying material and the assembly was exposed toultraviolet ray irradiation and then the exposed sheet was subjected toheat development at 150 C. for five seconds, with the result that a veryclear blue color image was obtained.

For comparison, a thermally developable copying material was prepared bysubstituting said P-dimethylamino- O-carboxy benzene diazoniumchloride-zinc chloride double salt with P-dimethylamino-benzenediazonium chloride. The obtained copying material had a too poor shelflife to be suitable for practical use. For example, the developedcopying material of the present invention was compared with the controlcopying material as to the fog density resulting from subjecting thesetwo to five day forced aging at 50C. and at a relative humidity of 20%.

The result was as follows:

Fog density Product of the present invention 0.12 Control 0.70

Example 2 Gr. P-benzoylamino O carboxy-benzene diazonium chloride-zincchloride double salt 1.0 NW-acid 2.5 Sodium trichloroacetate 3.0 Urea5.0

Thiourea Pyrophosphate Water 100.0

A solution having the above composition was applied onto the face of asupporting sheet and was dried in a manner similar to that described inExample 1, and thus a copying material having a markedly improved shelflife was obtained. The developed image on this print was bluish-violetin color, making a good contrast to the background.

For comparison, a thermally developable copying material was prepared bysubstituting said P-benzoylamino- O-carboxy-benzene diazoniumchloride-zinc chloride double salt with P-benzoylamino-benzene diazoniumchloride.zinc chloride double salt. The obtained copying material had atoo poor shelf life to be applicable for practical use.

Example 3 Gr. P-morpholino-m-ethoxy-O-benzene diazonium chloride-cadmiumchloride double salt 1.0 2,3-dihydroxy-naphthalene-6-sodium sulphonate2.5 Sodium trichloroacetate 3.0

Urea P ro hos hate Val ate i 100.0

A solution having the above composition was applied onto the face of asupporting sheet and dried in a manner similar to that described inExample 1, and a copying material having a markedly improved shelf lifewas obtained. The developed image on this copying material was sky-bluewhich was very clear.

For comparison, thermally developable copying materials were prepared bysubstituting said P-morpholino-methoXy-O-carboxy benzene diazoniumchloride-cadmium chloride double salt with P-morpholino-m-ethoXy-benzenediazonium chloride or with -P-morpholino-2,5-diethoxy-benzene diazoniumchloride-cadmium chloride donble salt. The obtained copying materialsdeveloped premature coupling at normal temperature, resulting in anextremely poor shelf life this making it not suitable for practical use.

Although particular preferred embodiments of the invention have beendisclosed for illustrative purposes, it will be recognized thatvariations or modifications of such disclosure, which come within thescope of the appended claims, are fully contemplated.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows;

1. In a thermally developable diazotype copying material having on onesurface of a supporting sheet a lightsensitive layer comprising alight-sensitive diazo compound, a coupler, a thermally decomposablealkali generating agent and an acid stabilizer, the improvement whereinsaid light-sensitive diazo compound consists of at least one double saltof a metal halide with a compound selected from the group consisting ofthe compounds of the following Formulas a through c,

(EJOOH wherein:

Y is selected from the group consisting of -CO-NH, S-, and --NH, and Xis selected from the group consisting of hydrogen, alkyl radicals having1 to 4 carbon atoms and alkoxy radicals having 1 to 4 carbon atoms;

(IIOOH wherein:

Y is selected from the group consisting of a morpholino radical, apyrrolidinyl radical and a piperazinyl radical, and

X is selected from the group consisting of hydrogen, alkyl radicalshaving 1 to 4 carbon atoms and alkoxy radicals having 1 to 4 carbonatoms; and

(IIOOH XII wherein:

Z is selected from the group consisting of alkoxy radicals having 1 to 4carbon atoms and X" is selected from the group consisting of halogen,alkyl radicals having 1 to 4 carbon atoms and alkoxy radicals having 1to 4 carbon atoms,

and said coupler is a member selected from the group consisting of 2,3dihydroXy-naphthalene-6-sodium sulfonate, 1-hydroxy-naphthalene-4-sodiumsulphate, lR-acid, naphthol AS, 2,3 dihydroxy-naphthalene, 2,7dihydroxy-naphthalene-3,6-disodium sulfonate and NW-acid,

the amounts of the diazo compound and the coupler being elfective toreact at temperatures in excess of about 100 C. to form a visible imageand the diazo compound and the coupler being substantially nonreactivein the presence of ammonia gas or an alkaline developing solution.

2. Improvement in a thermally developable diazotype copying materialaccording to claim 1, wherein said thermally decomposable alkaligenerating agent consists of at least on compound selected from thegroup consisting of urea, phenyl-urea, methyl-urea, ethyl-urea,hydroxyethyl-urea, acetyl'urea, 1,3-di1nethy1-urea, thiourea,thioacetamide, guanyl-O-methyl-isothio-urea, methyl-isothiourea,guanidine, amino-guanidine, guanyl-urea, biguanidine,methyl-biguanidine, O-methyl-guanyl-urea, cyanoguanidine, acetamide,acrylamide, propionamide, butylamide, malonamide, salicylamide, sodiumtrichloroacetate, potassium trichloroacetate, ammonium trichloroacetate,calcium trichloroacetate, dimethylamino-trichloroacetate,diethylamine-trichloroacetate, monomethylamine-trichloroacetate,triethanolamine-trichloroacetate, guanidine-trichloro acetate andamino-guanidine-trichloroacetate.

References Cited UNITED STATES PATENTS 1,807,761 6/ 1931 Spongerts 96-912,066,918 1/1937 Vonposer 96-91 X 2,532,126 11/1950 Slifkin 96-913,360,371 12/1967 Munder 96-91 3,434,838 3/1969 Munder 96-49 X WILLIAMD. MARTIN, Primary Examiner W. R. TRENOR, Assistant Examiner US. Cl.X.R.

